In process automation technology, field devices are often applied, which serve for registering and/or influencing of process variables. Examples of such field devices are fill level measuring devices, mass flow measuring devices, pressure and temperature measuring devices, etc., which register with corresponding sensors the process variables, fill level, flow, or temperature.
Serving for influencing process variables are so-called actuators, which, for example, in the case of valves, influence the flow of a liquid in a pipeline section, or, in the case of pumps, influence the fill level in a container.
Various field devices of such a sort are produced and sold by the members of the firm, Endress+Hauser.
As a rule, in modern automation technology plants, field devices are connected via fieldbus systems (HART, Profibus, Foundation Fieldbus) with superordinated units. These superordinated units serve, among other things, for process control or process visualizing.
Besides process control and process visualizing, fieldbus systems also serve for monitoring process plants. Monitoring of a plant can occur, for example, with the assistance of a corresponding process control unit (for example, Simatic S7 of Siemens). Process control units obtain plant-relevant data via telegrams, which are transmitted over the fieldbus in the course of regular (cyclic/scheduled) data traffic.
Fieldbus systems are, in given cases, integrated into enterprise networks, which work on the basis of Ethernet. Process or field device data can therewith be accessed from various areas of a company.
For worldwide communication, company networks can also be connected with public networks, e.g. the internet.
For servicing the field devices, corresponding operating programs are necessary. These operating programs can run self-sufficiently in a superordinated unit (FieldCare, Endress+Hauser; Pactware; AMS, Emerson; Simatic PDM, Siemens), but they can also be integrated into control system applications (Simile PCS7, Siemens; ABB Symphony; Delta V, Emerson).
The user would like to be able to service as many field devices as possible in the plant with a single operating program. Device-specific, especially manufacturer-specific solutions, for servicing are no longer accepted by users in this area of automation technology. Since the operating program does not know the parameters and the functionalities of a field device beforehand, these must be made known to the operating program. This occurs via device description files, which are made available by the field device manufacturers. As a rule, the current versions of the device description files are downloaded by the user via the Internet.
Device description files are not executable programs or program parts, and therefore also cannot directly be integrated into an operating program. They require an interpreter program, which is called up via the operating program and communicates with the operating program. The interpreter program interprets the device description file, and delivers to the operating program the needed information as parameters and/or functions of the field device. In given cases, device-specific graphical representations, which facilitate the servicing, are also delivered from the device description file.
In order to assure a safe servicing of the field devices, the device description files must be tested individually with the interpreter programs. Problematic in such case, however, is that the interpreter programs continue to be developed, and, so, are available in different versions.
Even though a device description file was successfully tested with an interpreter program, e.g. version 1.0, it is not automatically assured that the same device description file will also successfully run in a newer version 2.0 of the same interpreter program.
When a field device must be serviced, and the operating program does not permit an accessing of the parameters and functions of the field device because of problems concerning the interaction of the device description and interpreter program, this can prove very bothersome or unacceptable for the user. In the extreme case, these problems can lead to a plant shutdown of the entire process installation, which can result in considerable financial loss for the operator of the process installation.